API: Some raw message cleanup

[mediawiki.git] / includes / specials / SpecialEditWatchlist.php

<?php
/**
 * @defgroup Watchlist Users watchlist handling
 */

/**
 * Implements Special:EditWatchlist
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup SpecialPage
 * @ingroup Watchlist
 */

use MediaWiki\Linker\LinkRenderer;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MediaWikiServices;

/**
 * Provides the UI through which users can perform editing
 * operations on their watchlist
 *
 * @ingroup SpecialPage
 * @ingroup Watchlist
 * @author Rob Church <robchur@gmail.com>
 */
class SpecialEditWatchlist extends UnlistedSpecialPage {
        /**
         * Editing modes. EDIT_CLEAR is no longer used; the "Clear" link scared people
         * too much. Now it's passed on to the raw editor, from which it's very easy to clear.
         */
        const EDIT_CLEAR = 1;
        const EDIT_RAW = 2;
        const EDIT_NORMAL = 3;

        protected $successMessage;

        protected $toc;

        private $badItems = [];

        /**
         * @var TitleParser
         */
        private $titleParser;

        public function __construct() {
                parent::__construct( 'EditWatchlist', 'editmywatchlist' );
        }

        /**
         * Initialize any services we'll need (unless it has already been provided via a setter).
         * This allows for dependency injection even though we don't control object creation.
         */
        private function initServices() {
                if ( !$this->titleParser ) {
                        $lang = $this->getContext()->getLanguage();
                        $this->titleParser = new MediaWikiTitleCodec( $lang, GenderCache::singleton() );
                }
        }

        public function doesWrites() {
                return true;
        }

        /**
         * Main execution point
         *
         * @param int $mode
         */
        public function execute( $mode ) {
                $this->initServices();
                $this->setHeaders();

                # Anons don't get a watchlist
                $this->requireLogin( 'watchlistanontext' );

                $out = $this->getOutput();

                $this->checkPermissions();
                $this->checkReadOnly();

                $this->outputHeader();
                $this->outputSubtitle();
                $out->addModuleStyles( 'mediawiki.special' );

                # B/C: $mode used to be waaay down the parameter list, and the first parameter
                # was $wgUser
                if ( $mode instanceof User ) {
                        $args = func_get_args();
                        if ( count( $args ) >= 4 ) {
                                $mode = $args[3];
                        }
                }
                $mode = self::getMode( $this->getRequest(), $mode );

                switch ( $mode ) {
                        case self::EDIT_RAW:
                                $out->setPageTitle( $this->msg( 'watchlistedit-raw-title' ) );
                                $form = $this->getRawForm();
                                if ( $form->show() ) {
                                        $out->addHTML( $this->successMessage );
                                        $out->addReturnTo( SpecialPage::getTitleFor( 'Watchlist' ) );
                                }
                                break;
                        case self::EDIT_CLEAR:
                                $out->setPageTitle( $this->msg( 'watchlistedit-clear-title' ) );
                                $form = $this->getClearForm();
                                if ( $form->show() ) {
                                        $out->addHTML( $this->successMessage );
                                        $out->addReturnTo( SpecialPage::getTitleFor( 'Watchlist' ) );
                                }
                                break;

                        case self::EDIT_NORMAL:
                        default:
                                $this->executeViewEditWatchlist();
                                break;
                }
        }

        /**
         * Renders a subheader on the watchlist page.
         */
        protected function outputSubtitle() {
                $out = $this->getOutput();
                $out->addSubtitle( $this->msg( 'watchlistfor2', $this->getUser()->getName() )
                        ->rawParams(
                                self::buildTools(
                                        $this->getLanguage(),
                                        $this->getLinkRenderer()
                                )
                        )
                );
        }

        /**
         * Executes an edit mode for the watchlist view, from which you can manage your watchlist
         *
         */
        protected function executeViewEditWatchlist() {
                $out = $this->getOutput();
                $out->setPageTitle( $this->msg( 'watchlistedit-normal-title' ) );
                $form = $this->getNormalForm();
                if ( $form->show() ) {
                        $out->addHTML( $this->successMessage );
                        $out->addReturnTo( SpecialPage::getTitleFor( 'Watchlist' ) );
                } elseif ( $this->toc !== false ) {
                        $out->prependHTML( $this->toc );
                        $out->addModules( 'mediawiki.toc' );
                }
        }

        /**
         * Return an array of subpages that this special page will accept.
         *
         * @see also SpecialWatchlist::getSubpagesForPrefixSearch
         * @return string[] subpages
         */
        public function getSubpagesForPrefixSearch() {
                // SpecialWatchlist uses SpecialEditWatchlist::getMode, so new types should be added
                // here and there - no 'edit' here, because that the default for this page
                return [
                        'clear',
                        'raw',
                ];
        }

        /**
         * Extract a list of titles from a blob of text, returning
         * (prefixed) strings; unwatchable titles are ignored
         *
         * @param string $list
         * @return array
         */
        private function extractTitles( $list ) {
                $list = explode( "\n", trim( $list ) );
                if ( !is_array( $list ) ) {
                        return [];
                }

                $titles = [];

                foreach ( $list as $text ) {
                        $text = trim( $text );
                        if ( strlen( $text ) > 0 ) {
                                $title = Title::newFromText( $text );
                                if ( $title instanceof Title && $title->isWatchable() ) {
                                        $titles[] = $title;
                                }
                        }
                }

                GenderCache::singleton()->doTitlesArray( $titles );

                $list = [];
                /** @var Title $title */
                foreach ( $titles as $title ) {
                        $list[] = $title->getPrefixedText();
                }

                return array_unique( $list );
        }

        public function submitRaw( $data ) {
                $wanted = $this->extractTitles( $data['Titles'] );
                $current = $this->getWatchlist();

                if ( count( $wanted ) > 0 ) {
                        $toWatch = array_diff( $wanted, $current );
                        $toUnwatch = array_diff( $current, $wanted );
                        $this->watchTitles( $toWatch );
                        $this->unwatchTitles( $toUnwatch );
                        $this->getUser()->invalidateCache();

                        if ( count( $toWatch ) > 0 || count( $toUnwatch ) > 0 ) {
                                $this->successMessage = $this->msg( 'watchlistedit-raw-done' )->parse();
                        } else {
                                return false;
                        }

                        if ( count( $toWatch ) > 0 ) {
                                $this->successMessage .= ' ' . $this->msg( 'watchlistedit-raw-added' )
                                        ->numParams( count( $toWatch ) )->parse();
                                $this->showTitles( $toWatch, $this->successMessage );
                        }

                        if ( count( $toUnwatch ) > 0 ) {
                                $this->successMessage .= ' ' . $this->msg( 'watchlistedit-raw-removed' )
                                        ->numParams( count( $toUnwatch ) )->parse();
                                $this->showTitles( $toUnwatch, $this->successMessage );
                        }
                } else {
                        $this->clearWatchlist();
                        $this->getUser()->invalidateCache();

                        if ( count( $current ) > 0 ) {
                                $this->successMessage = $this->msg( 'watchlistedit-raw-done' )->parse();
                        } else {
                                return false;
                        }

                        $this->successMessage .= ' ' . $this->msg( 'watchlistedit-raw-removed' )
                                ->numParams( count( $current ) )->parse();
                        $this->showTitles( $current, $this->successMessage );
                }

                return true;
        }

        public function submitClear( $data ) {
                $current = $this->getWatchlist();
                $this->clearWatchlist();
                $this->getUser()->invalidateCache();
                $this->successMessage = $this->msg( 'watchlistedit-clear-done' )->parse();
                $this->successMessage .= ' ' . $this->msg( 'watchlistedit-clear-removed' )
                        ->numParams( count( $current ) )->parse();
                $this->showTitles( $current, $this->successMessage );

                return true;
        }

        /**
         * Print out a list of linked titles
         *
         * $titles can be an array of strings or Title objects; the former
         * is preferred, since Titles are very memory-heavy
         *
         * @param array $titles Array of strings, or Title objects
         * @param string $output
         */
        private function showTitles( $titles, &$output ) {
                $talk = $this->msg( 'talkpagelinktext' )->text();
                // Do a batch existence check
                $batch = new LinkBatch();
                if ( count( $titles ) >= 100 ) {
                        $output = $this->msg( 'watchlistedit-too-many' )->parse();
                        return;
                }
                foreach ( $titles as $title ) {
                        if ( !$title instanceof Title ) {
                                $title = Title::newFromText( $title );
                        }

                        if ( $title instanceof Title ) {
                                $batch->addObj( $title );
                                $batch->addObj( $title->getTalkPage() );
                        }
                }

                $batch->execute();

                // Print out the list
                $output .= "<ul>\n";

                $linkRenderer = $this->getLinkRenderer();
                foreach ( $titles as $title ) {
                        if ( !$title instanceof Title ) {
                                $title = Title::newFromText( $title );
                        }

                        if ( $title instanceof Title ) {
                                $output .= '<li>' .
                                        $linkRenderer->makeLink( $title ) . ' ' .
                                        $this->msg( 'parentheses' )->rawParams(
                                                $linkRenderer->makeLink( $title->getTalkPage(), $talk )
                                        )->escaped() .
                                        "</li>\n";
                        }
                }

                $output .= "</ul>\n";
        }

        /**
         * Prepare a list of titles on a user's watchlist (excluding talk pages)
         * and return an array of (prefixed) strings
         *
         * @return array
         */
        private function getWatchlist() {
                $list = [];

                $watchedItems = MediaWikiServices::getInstance()->getWatchedItemStore()->getWatchedItemsForUser(
                        $this->getUser(),
                        [ 'forWrite' => $this->getRequest()->wasPosted() ]
                );

                if ( $watchedItems ) {
                        /** @var Title[] $titles */
                        $titles = [];
                        foreach ( $watchedItems as $watchedItem ) {
                                $namespace = $watchedItem->getLinkTarget()->getNamespace();
                                $dbKey = $watchedItem->getLinkTarget()->getDBkey();
                                $title = Title::makeTitleSafe( $namespace, $dbKey );

                                if ( $this->checkTitle( $title, $namespace, $dbKey )
                                        && !$title->isTalkPage()
                                ) {
                                        $titles[] = $title;
                                }
                        }

                        GenderCache::singleton()->doTitlesArray( $titles );

                        foreach ( $titles as $title ) {
                                $list[] = $title->getPrefixedText();
                        }
                }

                $this->cleanupWatchlist();

                return $list;
        }

        /**
         * Get a list of titles on a user's watchlist, excluding talk pages,
         * and return as a two-dimensional array with namespace and title.
         *
         * @return array
         */
        protected function getWatchlistInfo() {
                $titles = [];

                $watchedItems = MediaWikiServices::getInstance()->getWatchedItemStore()
                        ->getWatchedItemsForUser( $this->getUser(), [ 'sort' => WatchedItemStore::SORT_ASC ] );

                $lb = new LinkBatch();

                foreach ( $watchedItems as $watchedItem ) {
                        $namespace = $watchedItem->getLinkTarget()->getNamespace();
                        $dbKey = $watchedItem->getLinkTarget()->getDBkey();
                        $lb->add( $namespace, $dbKey );
                        if ( !MWNamespace::isTalk( $namespace ) ) {
                                $titles[$namespace][$dbKey] = 1;
                        }
                }

                $lb->execute();

                return $titles;
        }

        /**
         * Validates watchlist entry
         *
         * @param Title $title
         * @param int $namespace
         * @param string $dbKey
         * @return bool Whether this item is valid
         */
        private function checkTitle( $title, $namespace, $dbKey ) {
                if ( $title
                        && ( $title->isExternal()
                                || $title->getNamespace() < 0
                        )
                ) {
                        $title = false; // unrecoverable
                }

                if ( !$title
                        || $title->getNamespace() != $namespace
                        || $title->getDBkey() != $dbKey
                ) {
                        $this->badItems[] = [ $title, $namespace, $dbKey ];
                }

                return (bool)$title;
        }

        /**
         * Attempts to clean up broken items
         */
        private function cleanupWatchlist() {
                if ( !count( $this->badItems ) ) {
                        return; // nothing to do
                }

                $user = $this->getUser();
                $store = MediaWikiServices::getInstance()->getWatchedItemStore();

                foreach ( $this->badItems as $row ) {
                        list( $title, $namespace, $dbKey ) = $row;
                        $action = $title ? 'cleaning up' : 'deleting';
                        wfDebug( "User {$user->getName()} has broken watchlist item ns($namespace):$dbKey, $action.\n" );

                        $store->removeWatch( $user, new TitleValue( (int)$namespace, $dbKey ) );

                        // Can't just do an UPDATE instead of DELETE/INSERT due to unique index
                        if ( $title ) {
                                $user->addWatch( $title );
                        }
                }
        }

        /**
         * Remove all titles from a user's watchlist
         */
        private function clearWatchlist() {
                $dbw = wfGetDB( DB_MASTER );
                $dbw->delete(
                        'watchlist',
                        [ 'wl_user' => $this->getUser()->getId() ],
                        __METHOD__
                );
        }

        /**
         * Add a list of targets to a user's watchlist
         *
         * @param string[]|LinkTarget[] $targets
         */
        private function watchTitles( $targets ) {
                $expandedTargets = [];
                foreach ( $targets as $target ) {
                        if ( !$target instanceof LinkTarget ) {
                                try {
                                        $target = $this->titleParser->parseTitle( $target, NS_MAIN );
                                }
                                catch ( MalformedTitleException $e ) {
                                        continue;
                                }
                        }

                        $ns = $target->getNamespace();
                        $dbKey = $target->getDBkey();
                        $expandedTargets[] = new TitleValue( MWNamespace::getSubject( $ns ), $dbKey );
                        $expandedTargets[] = new TitleValue( MWNamespace::getTalk( $ns ), $dbKey );
                }

                MediaWikiServices::getInstance()->getWatchedItemStore()->addWatchBatchForUser(
                        $this->getUser(),
                        $expandedTargets
                );
        }

        /**
         * Remove a list of titles from a user's watchlist
         *
         * $titles can be an array of strings or Title objects; the former
         * is preferred, since Titles are very memory-heavy
         *
         * @param array $titles Array of strings, or Title objects
         */
        private function unwatchTitles( $titles ) {
                $store = MediaWikiServices::getInstance()->getWatchedItemStore();

                foreach ( $titles as $title ) {
                        if ( !$title instanceof Title ) {
                                $title = Title::newFromText( $title );
                        }

                        if ( $title instanceof Title ) {
                                $store->removeWatch( $this->getUser(), $title->getSubjectPage() );
                                $store->removeWatch( $this->getUser(), $title->getTalkPage() );

                                $page = WikiPage::factory( $title );
                                Hooks::run( 'UnwatchArticleComplete', [ $this->getUser(), &$page ] );
                        }
                }
        }

        public function submitNormal( $data ) {
                $removed = [];

                foreach ( $data as $titles ) {
                        $this->unwatchTitles( $titles );
                        $removed = array_merge( $removed, $titles );
                }

                if ( count( $removed ) > 0 ) {
                        $this->successMessage = $this->msg( 'watchlistedit-normal-done'
                        )->numParams( count( $removed ) )->parse();
                        $this->showTitles( $removed, $this->successMessage );

                        return true;
                } else {
                        return false;
                }
        }

        /**
         * Get the standard watchlist editing form
         *
         * @return HTMLForm
         */
        protected function getNormalForm() {
                global $wgContLang;

                $fields = [];
                $count = 0;

                // Allow subscribers to manipulate the list of watched pages (or use it
                // to preload lots of details at once)
                $watchlistInfo = $this->getWatchlistInfo();
                Hooks::run(
                        'WatchlistEditorBeforeFormRender',
                        [ &$watchlistInfo ]
                );

                foreach ( $watchlistInfo as $namespace => $pages ) {
                        $options = [];

                        foreach ( array_keys( $pages ) as $dbkey ) {
                                $title = Title::makeTitleSafe( $namespace, $dbkey );

                                if ( $this->checkTitle( $title, $namespace, $dbkey ) ) {
                                        $text = $this->buildRemoveLine( $title );
                                        $options[$text] = $title->getPrefixedText();
                                        $count++;
                                }
                        }

                        // checkTitle can filter some options out, avoid empty sections
                        if ( count( $options ) > 0 ) {
                                $fields['TitlesNs' . $namespace] = [
                                        'class' => 'EditWatchlistCheckboxSeriesField',
                                        'options' => $options,
                                        'section' => "ns$namespace",
                                ];
                        }
                }
                $this->cleanupWatchlist();

                if ( count( $fields ) > 1 && $count > 30 ) {
                        $this->toc = Linker::tocIndent();
                        $tocLength = 0;

                        foreach ( $fields as $data ) {
                                # strip out the 'ns' prefix from the section name:
                                $ns = substr( $data['section'], 2 );

                                $nsText = ( $ns == NS_MAIN )
                                        ? $this->msg( 'blanknamespace' )->escaped()
                                        : htmlspecialchars( $wgContLang->getFormattedNsText( $ns ) );
                                $this->toc .= Linker::tocLine( "editwatchlist-{$data['section']}", $nsText,
                                        $this->getLanguage()->formatNum( ++$tocLength ), 1 ) . Linker::tocLineEnd();
                        }

                        $this->toc = Linker::tocList( $this->toc );
                } else {
                        $this->toc = false;
                }

                $context = new DerivativeContext( $this->getContext() );
                $context->setTitle( $this->getPageTitle() ); // Remove subpage
                $form = new EditWatchlistNormalHTMLForm( $fields, $context );
                $form->setSubmitTextMsg( 'watchlistedit-normal-submit' );
                $form->setSubmitDestructive();
                # Used message keys:
                # 'accesskey-watchlistedit-normal-submit', 'tooltip-watchlistedit-normal-submit'
                $form->setSubmitTooltip( 'watchlistedit-normal-submit' );
                $form->setWrapperLegendMsg( 'watchlistedit-normal-legend' );
                $form->addHeaderText( $this->msg( 'watchlistedit-normal-explain' )->parse() );
                $form->setSubmitCallback( [ $this, 'submitNormal' ] );

                return $form;
        }

        /**
         * Build the label for a checkbox, with a link to the title, and various additional bits
         *
         * @param Title $title
         * @return string
         */
        private function buildRemoveLine( $title ) {
                $linkRenderer = $this->getLinkRenderer();
                $link = $linkRenderer->makeLink( $title );

                $tools['talk'] = $linkRenderer->makeLink(
                        $title->getTalkPage(),
                        $this->msg( 'talkpagelinktext' )->text()
                );

                if ( $title->exists() ) {
                        $tools['history'] = $linkRenderer->makeKnownLink(
                                $title,
                                $this->msg( 'history_short' )->text(),
                                [],
                                [ 'action' => 'history' ]
                        );
                }

                if ( $title->getNamespace() == NS_USER && !$title->isSubpage() ) {
                        $tools['contributions'] = $linkRenderer->makeKnownLink(
                                SpecialPage::getTitleFor( 'Contributions', $title->getText() ),
                                $this->msg( 'contributions' )->text()
                        );
                }

                Hooks::run(
                        'WatchlistEditorBuildRemoveLine',
                        [ &$tools, $title, $title->isRedirect(), $this->getSkin(), &$link ]
                );

                if ( $title->isRedirect() ) {
                        // Linker already makes class mw-redirect, so this is redundant
                        $link = '<span class="watchlistredir">' . $link . '</span>';
                }

                return $link . ' ' .
                        $this->msg( 'parentheses' )->rawParams( $this->getLanguage()->pipeList( $tools ) )->escaped();
        }

        /**
         * Get a form for editing the watchlist in "raw" mode
         *
         * @return HTMLForm
         */
        protected function getRawForm() {
                $titles = implode( $this->getWatchlist(), "\n" );
                $fields = [
                        'Titles' => [
                                'type' => 'textarea',
                                'label-message' => 'watchlistedit-raw-titles',
                                'default' => $titles,
                        ],
                ];
                $context = new DerivativeContext( $this->getContext() );
                $context->setTitle( $this->getPageTitle( 'raw' ) ); // Reset subpage
                $form = new HTMLForm( $fields, $context );
                $form->setSubmitTextMsg( 'watchlistedit-raw-submit' );
                # Used message keys: 'accesskey-watchlistedit-raw-submit', 'tooltip-watchlistedit-raw-submit'
                $form->setSubmitTooltip( 'watchlistedit-raw-submit' );
                $form->setWrapperLegendMsg( 'watchlistedit-raw-legend' );
                $form->addHeaderText( $this->msg( 'watchlistedit-raw-explain' )->parse() );
                $form->setSubmitCallback( [ $this, 'submitRaw' ] );

                return $form;
        }

        /**
         * Get a form for clearing the watchlist
         *
         * @return HTMLForm
         */
        protected function getClearForm() {
                $context = new DerivativeContext( $this->getContext() );
                $context->setTitle( $this->getPageTitle( 'clear' ) ); // Reset subpage
                $form = new HTMLForm( [], $context );
                $form->setSubmitTextMsg( 'watchlistedit-clear-submit' );
                # Used message keys: 'accesskey-watchlistedit-clear-submit', 'tooltip-watchlistedit-clear-submit'
                $form->setSubmitTooltip( 'watchlistedit-clear-submit' );
                $form->setWrapperLegendMsg( 'watchlistedit-clear-legend' );
                $form->addHeaderText( $this->msg( 'watchlistedit-clear-explain' )->parse() );
                $form->setSubmitCallback( [ $this, 'submitClear' ] );
                $form->setSubmitDestructive();

                return $form;
        }

        /**
         * Determine whether we are editing the watchlist, and if so, what
         * kind of editing operation
         *
         * @param WebRequest $request
         * @param string $par
         * @return int
         */
        public static function getMode( $request, $par ) {
                $mode = strtolower( $request->getVal( 'action', $par ) );

                switch ( $mode ) {
                        case 'clear':
                        case self::EDIT_CLEAR:
                                return self::EDIT_CLEAR;
                        case 'raw':
                        case self::EDIT_RAW:
                                return self::EDIT_RAW;
                        case 'edit':
                        case self::EDIT_NORMAL:
                                return self::EDIT_NORMAL;
                        default:
                                return false;
                }
        }

        /**
         * Build a set of links for convenient navigation
         * between watchlist viewing and editing modes
         *
         * @param Language $lang
         * @param LinkRenderer|null $linkRenderer
         * @return string
         */
        public static function buildTools( $lang, LinkRenderer $linkRenderer = null ) {
                if ( !$lang instanceof Language ) {
                        // back-compat where the first parameter was $unused
                        global $wgLang;
                        $lang = $wgLang;
                }
                if ( !$linkRenderer ) {
                        $linkRenderer = MediaWikiServices::getInstance()->getLinkRenderer();
                }

                $tools = [];
                $modes = [
                        'view' => [ 'Watchlist', false ],
                        'edit' => [ 'EditWatchlist', false ],
                        'raw' => [ 'EditWatchlist', 'raw' ],
                        'clear' => [ 'EditWatchlist', 'clear' ],
                ];

                foreach ( $modes as $mode => $arr ) {
                        // can use messages 'watchlisttools-view', 'watchlisttools-edit', 'watchlisttools-raw'
                        $tools[] = $linkRenderer->makeKnownLink(
                                SpecialPage::getTitleFor( $arr[0], $arr[1] ),
                                wfMessage( "watchlisttools-{$mode}" )->text()
                        );
                }

                return Html::rawElement(
                        'span',
                        [ 'class' => 'mw-watchlist-toollinks' ],
                        wfMessage( 'parentheses' )->rawParams( $lang->pipeList( $tools ) )->escaped()
                );
        }
}

/**
 * Extend HTMLForm purely so we can have a more sane way of getting the section headers
 */
class EditWatchlistNormalHTMLForm extends HTMLForm {
        public function getLegend( $namespace ) {
                $namespace = substr( $namespace, 2 );

                return $namespace == NS_MAIN
                        ? $this->msg( 'blanknamespace' )->escaped()
                        : htmlspecialchars( $this->getContext()->getLanguage()->getFormattedNsText( $namespace ) );
        }

        public function getBody() {
                return $this->displaySection( $this->mFieldTree, '', 'editwatchlist-' );
        }
}

class EditWatchlistCheckboxSeriesField extends HTMLMultiSelectField {
        /**
         * HTMLMultiSelectField throws validation errors if we get input data
         * that doesn't match the data set in the form setup. This causes
         * problems if something gets removed from the watchlist while the
         * form is open (bug 32126), but we know that invalid items will
         * be harmless so we can override it here.
         *
         * @param string $value The value the field was submitted with
         * @param array $alldata The data collected from the form
         * @return bool|string Bool true on success, or String error to display.
         */
        function validate( $value, $alldata ) {
                // Need to call into grandparent to be a good citizen. :)
                return HTMLFormField::validate( $value, $alldata );
        }
}